Study On Control Strategy And Road Feeling For Steering-by-wire System

Along with the progress of the scientific technology, and the improvement of people’sliving standard, consumers are more and more concerning to the vehicle’s drivingperformance, The issuses that how to improve the vehicle handling stability, how to improvethe working conditions of the driver and how to reduce traffic accidents and so on, arebecoming increasingly prominent. In this trend, Steering-By-Wire System (SBW) haveemerged to meet this objective needs and it is a new developing generation of steeringsystems after EPS. Because it uses two motors instead of the mechanical connection betweenthe steering wheel and the road wheel, completely getting rid of the inherent limitations fromthe traditional system, furthermore the characteristics of angle and force transmissions arebeing randomly designed. This paper mainly researchs on the relevant aspects of thesteer-by-wire system features.Firstly, the structure and working principle of steer-by-wire system are analyzed in thispaper, and according to the most important characteristic of SBW—the transmission ratio ofrandom design, three methods of ideal steering ratio were introduced. The three controlprograms are brought into vehicle model and MATLAB/Simulink．Influence of variablesteering ratio control on vehicle handling stability is then analyzed，and the merits anddrawbacks of the three programs are compared. The simulation results showed that idealsteering ratio deduced by yaw rate and lateral acceleration synthesizes the other twoprograms，and has the best integral performance.Then effects of different vehicle state parameters feedback control strategy on handlingand stabilities of automobiles with SBW are researched. The simulation results showed thatsingle vehicle state feedback control strategy is difficult to satisfy the requirements ofSteering-By-Wire, though the total variance reducing by increasing the feedback coefficient,but steering characteristics can be better optimized and vehicle handling stability is improvedby application of full state feedback control strategy with appropriate cornering stiffnesscoefficient of change.Finally, depending on the road feel feedback characteristics of steer-by-wire system, thesimulation and the mathematical model of the target torque was established, meanwhile, the fuzzy adaptive PID controller was designed, in this case, they were simulated and analyzedbased on MATLAB/Simulink. The results of simulation indicate that the target torque whichwas established in this paper corresponds with the objective facts, and the designed fuzzyadaptive PID controller can achieve that the torque effectively track the target torque whichprovided by the road feel motor.